In the Setup from the Main Menu screen (Menu button twice quickly) select the Fitness icon. Once there, you can set everything up for yourself including enabling the Lap and specifying a Lap distance.
Once that is done, you can then customise the Data Fields on the map or compass screens and the Trip Computer (the Trip Computer will accommodate a whole different screen of data fields unlike the map or compass screens as there is more than one screen in the Trip Computer)
When on one of those screens,
1. Menu> Map Setup> Dashboard>Small Data Fields (if not already set)
2. The same for the Compass screen apart from just having the words 'Change Dashboard'
3. Menu>Change Data Fields>Data Field box becomes highlighted>Enter>at the bottom of the list 'Fitness'>whatever Data Field information you want showing